更新Ubuntu 20.04后 SSH连接不上，提示 Key exchange faild.

编辑/etc/ssh/sshd_config，在末尾添加如下配置：
KexAlgorithms curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1,diffie-hellman-group-exchange-sha1,diffie-hellman-group1-sha1
之后重启SSH服务：
systemctl restart sshd